Fractionation of free fatty acids



March 31, 1942# s. E. FREEMAN 2,278,309

' FRACTIONATION 0F FREE F-ATTY ACIDS Filed May 1'7, 1940 @RFF/#H75 ;-CaoL//va M50/0M i007m??- /3 20 1 l ha 2 *COLUMN de/ 57" ,qc Wvg Soz. VEA/'r I 00L .uk/v

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f77-.enc 7 gwue/rvboft STEPHEN E. FREE/wmv Patented Mar. 31, 1942 UNITED STATES PATENT OFFICE' i FRACTIONATION OF FREE FATTY ACIDS Stephen E. Freeman, Wauwatcsa, Wis., asslgnor to Pittsburgh Plate Glass Company, Allegheny County, Pa., a corporation of Pennsylvania.

Application May 17, 1940, Serial No. 335,793

11 Claims.

The present invention relates to a method of separating mixtures of a plurality of free fatty acids into fractions, each of which is relatively enriched in certain components of the mixture and correspondingly impoverished in other components, and it has particular relation'to the fractionation of such mixtures by liquid phase v extraction with a polar solventwhich is a more powerful solvent for certain components of the mixtures of acids than for others.

One object of the invention is to provide a process of solvent extraction for fractionation of mixtures of free fatty acids, by means of which it is possible to fractionate mixtures with polar solvents possessing such degree of miscibility with all components of the acid mixture asvto render it diflicult tomake a liquid phase fractionation by ordinary methods.

This and other objects of the invention will Vbe apparent from consideration of the following selective solvents disclosed in' the foregoing applications or similar solvents is somewhat dimcult because all components of the mixture possess such substantial degree of solubility in the solvents at Working temperatures as to mask the selectivity due to active polar groups and render it difficult to obtain immiscible phases.

It has now been found that in those cases where the selective solvent is strongly mlscible with all components of the oil, it may be combined'with a secondary relatively non-polar solvent, which is immiscible in said selective solvent.

to obtain separable phases of acids. The more active or polar components of the mixture of acids are more strongly attracted to the polar solvent than are the less active components so that there is considerable' degree of separation of the components of the mixture. In particular the process is applicable to the use of petroleum hydrocarbons, as secondary solvents. These are immiscible with many active polar solvents and are of low gravity so that separation into phases is rapid and relatively complete. Preferably the hydrocarbon is open chaifiand liquid at the operating temperatures. Isooctane is a goodv example of such solvent.

If .the petroleum hydrocarbonl and i a polar solvent immiscible therewith be conjointly contacted by agitation or countercurrent flow or other suitable method with a mixture of free fatty acids, such as are derivable by saponication of various glycerdeoils, including linseed oil, tung oil, soya bean oil, cottonseed oil, perilla oil, marine oils, such as menhaden, sardine, whale, cod and the like, lard, tallow, coconut oil, palm oil or to tall oil, it is possible to extract certain components upon the basisl of degree or y activity, due to differences in degree of unsaturae tion or differences in chain length. The acids are simply appropriately contacted with the polar and the non-polar solvents at a temperature at which thetwol solvents are immiscible, but all components remain in liquid state. Perhaps, as a result of the presence of double bonds in the unsaturates or of short chain length, some components of the mix are more polar than the saturated compounds or compounds of greater chain length, and have a greater affinity for the polar solvents. In other words they are more active with respect to the polar solvents.

As a resultthe system separates into two liquid phases, one consisting of a selective solvent containing a fraction relatively rich in active components of the acid mixture and the other consisting of petroleum hydrocarbon in which is dissolved a fraction relatively rich in less active saturates.

If the process be applied to the fractionation of free fatty acids of varying chain length such as obtained 4by the saponification of coconut oil or palm oil, it is found that the acids of relatively short chain length are preferentially dissolved in the selective polar solvent while the acids of longer chain length tend to remain in solution in the petroleum hydrocarbon. The liquid phases thus obtained may be separted from each .other by simply allowing them to settle for a suflicient period of time and then' drawing them olf into separate containers. It is also possible to make a separation by centrifugation in conventional apparatus. After the separation of the mixture, the solvents may be eliminated lby evaporation, crystallization, or other suitable methods.

It will be apparent that the process is'appliy'cable to batch-operation in which the free fatty acid mixture is simply agitated with the selective polar solvent and the :lmmiscible hydrocarbon in like and applied to the liquid phase extraction of the free acids herein enumerated or to similar Hygirozul, Carbonyl The ratio of active or polar solvent to hydrocarbon may vary over a range of from about 4 to 1 up to 10 or more of the latter to one of the former. 'I'he immiscible mixtures of selective polar solvent and hydrocarbon may be applied to the free fatty'acids in 4varying ratios. For example. in ratios from l to l up to a ratio of 10 or `12 parts of the solvent mixture to l part of acid. In general it is possible by increasing the temperature to obtain complete miscibility of almost any of the systems herein disclosed. Conversely, they can be lcooled to effect splitting into liquid phases, which can be separated from each other. The miscibility temperature for different systems will vary, but can easily be determined for a given system by cooling a miscible system until a cloud lappears. The division or removal of the fractions, preferably is effected at a temfre acids:

Tablon 5.

Hyo'rmz. mm-DmnuBom-Emor Methyl alcohol Methyl fui-oste Ethylelsne glycol1 Furfuryl acetate Pro ene g yco f Glygne En, Hozom Meth lchloroaoetste Hlldfmlr En betahloroethyl acetate beta-H inxytr ethyl acetate Acetochlorhydrln Methy ac a e u Ethyl lactate E* f CWM@ Dlacetin Methyl cyanoscetate Amino (or Imno) th lbutanolone Diethylene trlamlne v 1ieeety methyl carblnol Trlethylene tetramine 30 Hvdroxyl, Ether 1 Amino (or Imi'no), Double Methyl Cellosolve'(bmethoxy BWM? ethanol) Anillne Dlethylene gl col Toluidlne Trlethylene g ycol mme Carbltl 2-Hydroxy methyl-l, 3-dioxo- Propionitrlle lane' v Sulfate Carbozul l Dimethyl sulfate Formlc acid Acetlc acid lgggd Btaldeh de Hoarmz, Double Bona., Fumf Y 40 Phenol 'Clnnamaldehyde Benzyl alcohol Benzaldehyde m-Nltrobenzaldehyde Hydroul, Triple Banda C b l Dlmethyl cthynyl carblnol a' my H d l Haz m Acetonyl acetone sfoggio ohloydrln CMMI/Z Ethf Dmbl Bonds 45 Propylene chlorhydrin Furfural acetone gefohmma'dlbmmo pmpyl Carbom/Z, Double Bonds H d l om Benzal acetone 1/ roxy er i beta-Hydroxy roplonitrile Carboni/11AM beta-Ethoxy et yl lactate F Ol'mmide 50 beta-Ethoxy ethyl glycolate Acetamide ggggl 81001101 carbonyl, C'hloro Balicylaldehyde (aldehyde, dou- 1ch1or butanone-Z ble bond) Ether 2-Nltro-l-butanol 2Nitro-2methyl-3-hexanol Dimethoxy tetreglycol 55 Acid Anm/iride Eihtr, C'hlora Acetlc betta??1 b eta'-Dlchloro diethyl e er Eater Chloroethoxy chlorethyl other gthyletrii glycol diformate Ether Imm nace gl col diieltalte l t Morphollne Y 80B E yco a e Eth lidinadiacetatc Ether' N "0 Met yl malonste o-Nitro anisole Ethl oxalate oNitro phenotole Met y1 oxalate Ether, Caman Eder, Carboni/1 beta-Methoxy ethyl carbonate 65 Methyl levnlinate Nm Eth llevullnate Met yl acetoacetate Nitl'omethane Ethyl scetoacetate Nitmbenzene nu", Een" WMI/male egy geosove (tg-Fatte Methyl thiocyanate o e y eosovea pac a Dimethyl Cellosolve succinate Phosphat! Trlmethyl phosphate Eder, Imdo v Triethyl phosphate Ethyl n-methyl carbamate Eder, double bond Y Ethyl mslete phere.

perature somewhat below that'of complete miscibility,but above that which the components tend to separate by crystallization. .In general the division should be effected within a range of about 2 to 40 C. below that of complete miscibili'ty of the system. As the system of acids and solvents approach the temperatures of complete miscibility, it will be apparent that the fcomponents go more and more into solution in each other, but so long as the phases Separate it is possible to effect some degree of fractionation. The degree of fractionation desired in any particular mixture of acids will depend upon the characteristics desired in the fractions. In some cases a small degree of fractionation is suicient. In other cases relatively marked differences between one or more components and the original acid mixture may be desired. Such separation can be attained by appropriate reduction of the temperature of the system. Such reduction, of course, is attended by corresponding reduction of the yield of the desired component.

In my copending applications above referred to the addition of water to the selective solvent in order to reduce miscibility at low temperatures of the relatively saturated or long chain component of a glyceride oil mixture is referred to. The same principles may be applied to the extraction of the free fatty acids derived from the oil. Manifestly this principle is of particular applicability to thefractionation of glyceride oil acids with a solvent which possesses a substantial degree of solubility with water. Examples of such Water soluble polar solvents are furfural and the various alcohols including methyl, ethyl alcohol, ethylene glycol, propylene glycol and glycerin. To these water may be added in varying amounts, for example, of from 1 to 15 per cent. In general the addition of Water tends substantially to increase the temperature at which the glyceride oil acids and the polar solvent becomecompletely miscible in each other. In some cases this is of advantage because it permits the operation of the system at a temperature substantially above that of the 'atmos- This is sometimes desirable because it obviates cooling of the systemin order to obtain separationof the liquid phases, and also because it is easier to maintain substantially constant working conditions at an elevated temperature than at a low temperature.

It is also possible to' admix two or more of the selective polar solvents with each other and to admix non-selective polar solvents at least in limited amounts with the system.

'Ihe following constitutes specific examples of f' ture and allowed to separate into layers. solvents were then distilled off from the two the application of the principles of the invention to acid mixtures:

Parts by volume The fractions separately under vacuum Iodine value of original acid 173 Iodine value of acid in hydrocarbon A 166 Iodine value of acid in furfural 193 A 30 per cent mixture of linseed oil fatty acids in the same hydrocarbon was agitated with'l volume of furfuryl alcohol and separated into fractions at room temperature.

Iodine value of original acid 173 Iodine value of acid in hydrocarbon 162 Iodine value of acid in solvent 203 Ethylene glycol diacetate was agitated at room temperature with a 12 per cent by volume mixture of linseed oil fatty acids in petroleum ether, and the mixture was separated into fractions from which the solvents were eliminated.

Iodine value of original acids 173 Iodine value of acids in hydrocarbon 168 Iodine value of acids in solvent 175 Free fatty acids. may be subjected to repeated stages of extraction with the hydrocarbon in order to remove additional amounts of the less active constituents therefrom. .In the case of ,mixtures containing unsaturated acids it is possible by application of a relatively few stages of washing the hydrocarbon to obtain the substantially pure acid. The following flow diagram illustrates the treatment of free fatty acids with a mixture of furfural in a series of stages:

In conducting the extraction the free fatty acids of soya bean oil were dissolved in petroleum naphtha to obtain a 50% solution of volume of free fatty acids. This solution was extracted by agitating with furfural which had previously been saturated with petroleum naphtha at room temperature (approximately 23 C.). Theratio of furfural to fatty acid solution was l to 1; The

raiiinate was reextracted with furfural saturated with naphtha repeatedly keeping the ratio of furfural to `fatty acid solution in the relation of 1 'to 2.

The extract -solution was simply contacted with an additional equal volume of petroleum naphtha at each stage and separation repeated. The iodine values for each extract is indicated by the numeralsvin the diagram.

The raffinate phases were contacted with additional furfural to split out further fractions of A,relatively high iodine value. used as such or can be returned to the original or feed acids or to one of the other fractions on the extract side-of the system having the same or nearly the same iodine value. For example,

`fractions 7 and 5' might be returned to the feed acids, 2' might be combined with 1, 4 with 5, 6' with 3. 4 with 6 and 5 with 7.

This repeatedextraction of the free fatty acids is substantiallyl analogous to back washing free fatty Iacids in countercurrent flow to a solvent in a suitable column. Such apparatus and process are illustrated diagrammatically in the drawing in which an extraction column I0 is provided with jacket sections II, having inlets I2 and outlets I3 for temperature control'medium.

A hydrocarbon diluent such as petroleum naphtha is introduced into the column a short distance above the lower extremity through conduit I4, and a free fatty acid mixture, such as soya bean oil acids, cottonseed acids, coconut oil acids, or others of like nature, is fed to an intermediate portion of the column at ay substantial distance above the inlet I4 through conduit I6. 'Ihe latter may be encased in a heating jacket I1 having inlet I8 and outlet I9 for a heating fluid. y It is, also, permissible to admix the hydrocarbon and the oil or oil acids and introduce them `simultaneously into column Ill through conduit I6. Active solvents such as furfural or one of the other solvents herein disclosed may be introduced a short distance from the upper extremityof the column through conduit I9.

It is to be observed that the raffinate phase comprising the less active or more highly saturated orV longer chain length fatty acids dissolved in the outer carbon collect as a layer 23 in the upper extremity of the column while the extract comprising the active polar solvent saturated with more active acids collects as a distinct liquid layer 24 in' the lower portion of the column. Between these two layers' there is an extensive zone 26 filled with countercurrently owing mixtures of oil, hydrocarbon and free fa-tty acids in varying degrees of saturation with each other. Extract is drawn off at the lower extremity `through conduit 21 andrainate isv drawn out at the upper extremity through conduit 28, or in differences in the average chain length of the.

molecule. The shorter chain lengths tend to go into the polar solvent more strongly than do the longer chain lengths.

In the fractionation of coconut oil glycerides the oil was first dissolved in an equal volume of petroleum hydrocarbon, e. g. petroleum naphtha and one volume of the mixture was treated V with four volumes of anhydrous furfural, at a temperature of about 20 or 25 C. With furfural saturated or at least partially saturated with These can bewater it is possible to increase the temperature of treatment several degrees. The solvents, when left to stand, separated into liquid layers that could be drawn off into separate containers.

The solvents were then eliminated by vacuum distillation. The rafiinate fraction (that dissolved in the naphtha) had a substantially higher melting point than the original oil or that extracted by the furfural. Conversely the melting point of the extract from the furfural was substantially lower than that of the original oil. Apparently separation had been upon the basis of chain length.

In the case of more highly unsaturated glyceride oils, such as tung oil, linseed oil, fish oil, soya bean oil, cotton-seed and others herein enumerf ated, the more unsaturated or actively unsaturated components are extracted preferentially acids dissolved therein.

2. A process of extracting a relatively Aactive fraction from a mixture of free fatty acids comprising such active fatty acid in adnfixture with less active fatty acid, which process comprises contacting the mixture with a two phase solvent system comprising a relatively non-polar hydrocarbon solvent and an active polar solvent im miscble therewith, the free. fatty acids being passed in at an intermediatey point in the. length of a column, polar solvent being passed in above the inlet for free acids and non-polar solvent being passedin at a point below the inlet for free acids, the immiscible solvents carrying respective components dissolved` therein.I being withdrawn at 'opposite ends of the column.

3.*A`process of extracting a relatively active fraction from a mixture of free fatty acids comj 6. A process as defined in claim 1 in which the l polar solvent is furfural and the non-polar sol-- vent is a parailinc hydrocarbon..

'1. A process as dened in claim l in whichA the non-polar solvent is iso-octane.

8. A process of extracting a relatively active fraction from a mixture of free fatty acids comprising such active fatty' acid in adniixture with less active fatty acid, which process comprises contacting the mixture with a two phase solvent system comprising a relatively non-polar hydro-l carbon solvent and an active polarsolvent, im-

miscible therewith, said polar solvent containing a substantial amount of water, separating the solvents'and freeing them from the free acids dissolved therein.

9. A process as defined in claim 3 in which the acids 'are those from. oils of a class consisting of marine oil, soya bean oil, linseed oil perilla oil,..

tung oil, cottonseed oil, coconutoil, lard, tallow and 'tall oil. 1

10. A process as defined in claim 14 which the polar solvent is wet furfural and the hydro' carbon is isooctane.-

11. A process as defined in claim 1 in which Y thegfree acids treated are' those from an oil of 

